In power systems, circuit breakers are used for connecting and disconnecting a load. During this process, the active elements of the circuit breaker either interrupt or incept high current, causing stresses in the circuit breaker as well as the connected power system components. The flow of the high current can be limited by closing and opening the circuit breaker at a specific instance on the source voltage waveform. A plurality of techniques are known for controlling the opening or closing of the circuit breaker in order to prevent generation of transient phenomenon. Such techniques rely on the usage of devices that perform synchronized switching control. One such device is the point on wave controller.
Point on wave controller is used for controlling the switching instance of the circuit breaker. On receiving a command from a control unit, the point on wave controller advances the command to achieve closing or opening at an instance to minimize the current. The point on wave controller detects the opening or closing actuation time (also referred to as operating time) of the circuit breaker and calculates a time for switching in respect of the opening or closing command of the circuit breaker to ensure switching on a particular point on the voltage waveform in a corresponding phase. The point on wave controller determines the electrical operating time as the time period between the instance at which the command was given to the circuit breaker and the instance at which electrical switching (i.e. interruption or inception of the electrical connection) happened in a corresponding phase.
Conventionally, for detecting switching instance in a phase, the point on wave controller relies on current measurements from that phase from a current sensor connected to the load. In a multiphase electrical system, current in the plurality of phases of the multiphase electrical system is monitored using one or more current transformers. Based on the current feedback from the plurality of phases, the point on wave controller determines a plurality of instances of switching in the plurality of corresponding phases.
However, when a current feedback is not available for a particular phase, instance of switching cannot be detected in that phase. Therefore, when a current transformer which measures the current in that phase is unavailable, for example due to fault or has become unreliable, the point on wave controller is not able to detect any instance of switching in that phase and is unable to determine the electrical operating time of the circuit breaker in that phase. In absence of relatively accurate electrical operating time of the circuit breaker in a phase, point on wave switching cannot be adapted for correcting errors in such scenarios.
Additionally, for monitoring current in the phases, a plurality of current transformers have to installed in the phases and these current transformers have to connected to the controller via appropriate wired or wireless connections. This requires substantial investment and effort during installation.
Therefore, in light of the abovementioned discussion, there is a need for a method and system that address the issues mentioned above.